The present invention relates to a fuel injector for supplying atomized fuel to an internal combustion engine, and more particularly to such a fuel injector improved in fuel atomization.
In general, it is desirable to finely particulate or atomize the fuel to be supplied to the engine, so as to improve a fuel combustion efficiency, which contributes to an improvement in fuel consumption and emission control.
It is known that a fuel colliding member for atomizing a columnar fuel injected from a fuel injection hole of the fuel injector is positioned in alignment with the fuel injection hole in front thereof. By the provision of the fuel colliding member as mentioned above, the columnar fuel injected from the fuel injection hole collides with the fuel colliding member to be finely particulated or atomized.
The fuel colliding member is formed in various shapes such as circular, spherical and conical shapes (see Japanese Utility Model Laid-open Publication Nos. 57-152458 and 58-90365, for example). In the conventional fuel colliding member having any shape, a size in cross section perpendicular to an axis of the fuel injector is larger than that of the fuel injection hole, so that all the parts of the columnar fuel injected from the fuel injection hole collide with the fuel colliding member to be atomized.
FIG. 1A shows an example of the prior art fuel injector, in which it is appreciated that a columnar fuel F injected from a fuel injection hole 6 entirely collides with a fuel colliding member 34A to be atomized.
The present inventors have investigated to find that when an outer diameter .phi.a of the fuel colliding member 34A is larger than a diameter .phi.d of the fuel injection hole 6, all the columnar fuel is sufficiently atomized by the collision with the fuel colliding member 34A, but the atomized fuel is diffused radially outwardly to be deposited onto an inner wall surface 22 of a nozzle 21, resulting in insufficient atomization of the fuel to be sprayed from the nozzle 21. Furthermore, it has been also found that a velocity of the atomized fuel to be sprayed from the nozzle 21 is reduced to elongate a time for making the atomized fuel reach the engine.